Sheet processing apparatus and image forming apparatus

ABSTRACT

A sheet processing apparatus and an image forming apparatus can secure the stackability of a sheet when discharging a residual sheet. When a residual sheet is conveyed from a main body of an image forming apparatus to a first sheet stacking portion at turning on the power for the main body of the image forming apparatus, the trailing edge of the residual sheet is aligned first by a trailing edge aligning portion. And then, a residual sheet is moved to a sheet discharging position, in which the sheet is discharged onto a second sheet stacking portion, while the residual sheet, the trailing edge of which has been aligned, is being held by a holding member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet processing apparatus and an image forming apparatus, particularly to a sheet processing apparatus and an image forming apparatus capable of discharging a residual sheet at turning on the power.

2. Description of the Related Art

Heretofore, some of image forming apparatuses such as a copying machine, a printer and a facsimile are provided with a sheet processing apparatus for relieving troublesome tasks required to perform such treatments as a stapling treatment and a punching treatment on sheets with images formed thereon. The sheet processing apparatus is designed to sequentially receive sheets with images formed thereon into the apparatus and selectively perform such treatments as the stapling treatment and the punching treatment on the sheets.

Now, the image forming apparatus, which is provided with such a sheet processing apparatus, performs initialization control at turning on the power such as driving-gear engagement check, high-transfer-voltage control, and scanner motor drive check. Then, after the treatments have been performed by such initialization control, the image forming apparatus enters into a standby mode, starts feeding sheets when receiving a printing request from external equipment connected, and performs image forming operation in accordance with a predetermined electrophotographic process.

Incidentally, a controlling portion of the image forming apparatus is adapted to control the apparatus, when detecting any residual sheets within a main body of the image forming apparatus at turning on the power, to enter into a jam clearance mode and wait for a predetermined jam clearance operation to be performed by a user.

Then, thereafter when, for example, a sensor detects that a door for jam clearance has been opened and closed by the user to perform the jam clearance, and a signal is transmitted to the controlling portion of the image forming apparatus through a sensor input portion, the controlling portion detects that the jam clearance has been performed based on the door open/close information. When the jam clearance has been completed by the user and the power is turned on again, the above-described initialization control is carried out and the apparatus enters into the standby mode.

On the other hand, as a conventional image forming apparatuses, there is one designed such that a sheet presence/absence detecting means is disposed in a sheet conveying path to detect a presence or absence of a residual sheet in the sheet conveying path, when carrying out the initialization operation to cause an image forming means to enter into a standby mode for enabling the image forming operation at turning on the power. Such image forming apparatus is designed so that, when any residual sheet is detected by the sheet presence/absence detecting means, the residual sheet is conveyed to a sheet processing apparatus during the initialization operation and discharged to a sheet discharge tray of the sheet processing apparatus (for example, refer to Japanese Patent Application Laid-Open No. H08-286586).

Now, when the residual sheet is conveyed as described above, the conventional sheet processing apparatus is designed to discharge the residual sheet to the sheet discharge tray, and is designed to convey and discharge the conveyed sheet in accordance with the sheet discharging speed of the main body of the image forming apparatus.

However, when a sheet is thus discharged in accordance with the sheet discharging speed of the main body of the image forming apparatus, a size of the sheet to be discharged is unknown. Therefore, for example, in the case where the sheet discharging speed is too fast relative to the sheet size, the sheets are unevenly stacked on the downstream side in the sheet discharge direction on the sheet discharge tray. Also, when the sheet is conveyed in a skewed state from the main body of the image forming apparatus, the sheet is stacked on the sheet discharge tray in the skewed state as is.

That is, since the conventional sheet processing apparatus, when discharging a residual sheet, discharges the sheet synchronously with the sheet discharging speed of the main body of the image forming apparatus without correcting the skew feed, stackability of sheet on the sheet discharge tray cannot be secured.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-described present situation. An object of the present invention is to provide a sheet processing apparatus and an image forming apparatus capable of securing stackability of a sheet when discharging a residual sheet.

An object of the present invention is to provide a sheet processing apparatus comprising: a first sheet stacking portion connected to a main body of an image forming apparatus for stacking thereon a sheet conveyed from the main body of the image forming apparatus; a second sheet stacking portion provided downstream of the first sheet stacking portion with respect to a sheet conveying direction for stacking thereon the sheet discharged from the first sheet stacking portion after being treated thereon; a trailing edge aligning portion for aligning a trailing edge in the sheet conveying direction of the sheet stacked on the first sheet stacking portion; a discharging member having a holding member for holding the sheet, the trailing edge of which has been aligned by the trailing edge aligning portion, and while holding the sheet by the holding member, moving the sheet to a sheet discharging position, in which the sheet is discharged onto the second sheet stacking portion by releasing the holding by the holding member; and a control device for controlling the discharging member in such a manner that, when a residual sheet remains in the main body of the image forming apparatus and the residual sheet is conveyed at turning on the power for the main body of the image forming apparatus, the trailing edge of the residual sheet is aligned by the trailing edge aligning portion, and then the discharging member is moved to the sheet discharging position while holding the residual sheet by the holding member.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the construction of an image forming apparatus provided with a sheet processing apparatus according to an embodiment of the present invention.

FIG. 2 illustrates the construction of the sheet processing apparatus.

FIG. 3 shows a manner in which a sheet is discharged onto a treatment tray of the sheet processing apparatus.

FIG. 4 illustrates a driving mechanism for an offset roller and a conveying roller of the sheet processing apparatus.

FIG. 5 illustrates a driving mechanism for the offset roller, the conveying roller, a sheet bundle discharging member and a sheet clamp member of the sheet processing apparatus.

FIGS. 6A and 6B illustrate the operation of the offset roller and the resultant movement of the sheet.

FIG. 7 illustrates the operation of the sheet clamp member.

FIG. 8 shows a manner in which the sheet bundle discharging member discharges a sheet bundle onto a stack tray.

FIG. 9 is a block diagram showing the construction of a controlling portion of the sheet processing apparatus.

FIG. 10 is a flow chart illustrating a part of the sheet processing operation of the sheet processing apparatus and a main body of the image forming apparatus at turning on the power.

FIG. 11 is a flow chart illustrating the remainder of the sheet processing operation of the sheet processing apparatus and the main body of the image forming apparatus at turning on the power.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be hereinafter described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing a construction of an image forming apparatus provided with a sheet processing apparatus according to an embodiment of the present invention. FIG. 1 shows an image forming apparatus A, a main body 500 of the image forming apparatus, an automatic original feeder (ADF) 300 installed on an upper face of the main body 500 of the image forming apparatus and a sheet processing apparatus 400 that processes sheets discharged from the image forming apparatus A.

In addition, in FIG. 1, a reader portion (image inputting device) 120 converts an image of an original into image data. A printer portion 200 which is an image forming portion has a plurality of types of sheet cassettes 204 and 205, and outputs the image data as a visible image onto a sheet by a print command.

When in the image forming apparatus A of such a construction, an image of an original is to be read to thereby form an image, originals stacked on the automatic original feeder (ADF) 300 are adapted to be first conveyed sequentially one by one onto a platen glass surface 102.

Next, when the original is thus conveyed to a predetermined position on the platen glass surface 102, the lamp 103 of the reader portion 120 is turned on and a scanner unit 101 is moved and irradiates the original. Reflected light from this original is inputted to a CCD image sensor portion 109 through the intermediary of mirrors 105, 106, 107 and a lens 108, and electrical processing such as photoelectric conversion is effected in this CCD image sensor portion 109, and ordinary digital processing is effected.

Next, the image signal thus subjected to the electrical processing is converted into a modulated optical signal by the exposure controlling portion 201 of the printer portion 200, and irradiates a photosensitive drum 202. By this irradiating light, a latent image is formed on the photosensitive drum 202, and this latent image is developed by a developing device 203 with a result that a toner image is formed on the photosensitive drum 202.

Next, in timed relationship with the leading edge of this toner image, a sheet S is conveyed from the sheet cassette 204 or 205, and in a transferring portion 206, the toner image is transferred to the sheet S. Thereafter, the toner image transferred to the sheet S is fixed by a fixing portion 207, and after the toner image has been thus fixed, the sheet S is discharged from a sheet discharging portion 208 to the outside of the image forming apparatus.

Then, the sheet S outputted from the sheet discharging portion 208 is conveyed to the sheet processing apparatus 400, where a treatment such as sorting or stapling is effected in accordance with an operating mode designated in advance.

When images successively read in are to be outputted onto the two sides of a sheet S, the sheet S on one side of which the toner image has been fixed by the fixing portion 207 is first directed to a path 215 by a changeover member 209 being once changed over to a solid-line direction in FIG. 1, and is conveyed to a surface reverse path 212 via a path 218 by a direction changeover member 217 being changed over to a broken-line and a direction changeover member 213 being changed over to a broken-line direction.

Next, after the trailing edge of the sheet has passed the direction changeover member 213, the direction changeover member 213 is changed over to a solid-line direction, and the rotational direction of a roller 211 is reversed to thereby direct the sheet to a path 210, whereafter the sheet is conveyed to the transferring portion 206 so that an image may be formed on the back side of the sheet S.

On the other hand, the sheet processing apparatus 400 is provided with a stapling function which is a binding operation by the stapler unit, in addition to a sorting operation of sorting the sheet. As shown in FIG. 2, the sheet processing apparatus 400 is provided with a treatment tray 410 for treating the sheets S successively discharged from the main body 500 of the image forming apparatus, and a stack tray 421 for finally stacking thereon the sheet bundle treated on the treatment tray 410. The sheet processing apparatus 400 is constructed to form a sheet bundle of the number of sheets corresponding to the number of originals on the treatment tray 410 exemplified as a first sheet stacking portion and discharge each sheet bundle to the stack tray 421 exemplified as a second sheet stacking portion.

In FIG. 2, a sheet receiving portion 401 receives the sheet S discharged from the main body 500 of the image forming apparatus. The sheet S received by this sheet receiving portion 401 is detected by an entrance sensor 403, and thereafter is conveyed by a conveying roller 405 and an offset roller 407, and thereafter, as shown in FIG. 3, is discharged onto the treatment tray 410. The sheets S thus stacked on the treatment tray 410 have their presence or absence detected by a sheet bundle discharge sensor 415 shown in FIG. 2.

The entrance sensor 403 is a sheet detecting device for detecting the trailing edge of the sheet S conveyed from the main body 500 of the image forming apparatus.

The offset roller 407 is held for upward and downward movement by an offset roller arm 406 movable in a vertical direction about a shaft 406a shown in FIGS. 4 and 5. This offset roller 407, when it conveys the sheet S to the treatment tray 410, is adapted to be moved to an upper position through the offset roller arm 406, whereby the sheet S is conveyed onto the treatment tray 410 without being hindered by the offset roller 407.

This offset roller arm 406 is movable up and down with the shaft 406 a as a fulcrum by the pickup solenoid 433. That is, the offset roller 407 is moved up and down by the ON/OFF of the pickup solenoid 433 through a down lever 433 a.

Also, this offset roller 407, as shown in FIG. 5, is adapted to be driven by a conveying motor 431 which drives the conveying roller 405, through belts 431 a and 431 b, and when the conveying motor 431 is rotated, the offset roller 407 is adapted to be rotated in the conveying direction, or rotated in a direction reverse to the conveying direction (hereinafter referred to as the reverse rotation), by an amount according to the amount of rotation of the conveying motor 431.

Incidentally, in this embodiment, the pickup solenoid 433 is turned off before the sheet S has passed through the conveying rollers 405. That is, timing when the pickup solenoid should be turned off is prescribed based on the movement amount of the sheet from the entrance sensor 403 (in the embodiment, 80 mm). Thereby, the offset roller 407 moves down with the aid of the gravitational force of the offset roller 407 and lands on the sheet, and thereafter is adapted to be rotated in the sheet conveying direction for a predetermined time, and to be reversely rotated when a predetermined time further elapses.

By the offset roller 407 being thus reversely rotated, the trailing edge of the sheet is abutted against a sheet trailing edge stopper 411 exemplified as a regulating member provided upright on the upstream end portion of the treatment tray 410 with respect to the conveying direction for regulating the trailing edge of the sheet S.

Incidentally, in this embodiment, a trailing edge aligning portion 408, which aligns the trailing edge in the sheet conveying direction of the sheet stacked on the treatment tray 410, is composed of the offset rollers 407 exemplified as a sheet conveying member, which can rotate forward and reversely, and the sheet trailing edge stopper 411. The sheet S is aligned in the conveying direction by the trailing edge aligning portion 408.

A positioning wall 416 as a side edge regulating member shown in FIG. 4 regulates the position of the edge portion in a direction orthogonal to the sheet conveying direction of the sheet (hereinafter, referred to as width direction). A stapler unit 420 as a binding means is disposed near the positioning wall 416 of the treatment tray 410 and performs stapling treatment on a sheet bundle formed on the treatment tray 410.

Incidentally, the offset rollers 407 move in the width direction being driven by an offset motor 432 as a driving means, which can rotate forward and reversely, through a rack 406 c and a pinion 406 b. Thereby, the offset rollers 407 are adapted to come closer to the positioning wall 416 or moves away therefrom. The offset motor 432 constitutes a moving means together with the offset rollers 407.

Design is made such that when the offset roller 407 thus approaches the positioning wall 416, the sheet abutted against the sheet trailing edge stopper 411 and aligned in the conveying direction is moved to the positioning wall 416 by the frictional force of the offset roller 407 and the positioning thereof in the width direction is effected. After the sheet S has been abutted against the positioning wall 416, the offset roller 407 is adapted to be slidingly moved on the sheet and stopped.

Here, by such an offset roller 407 being provided, the sheet discharged onto the treatment tray 410 is conveyed to the stack tray side by the offset roller 407 rotated in the sheet conveying direction, as shown in FIG. 6A, whereafter as shown in FIG. 6B, the sheet is returned to the sheet trailing edge stopper 411 by the reverse rotation of the offset roller 407, and thereafter has its trailing edge abutted against the sheet trailing edge stopper 411 and is aligned.

In FIGS. 6A, 6B and 7 which will be described later, unlike FIG. 4 already described, description is made by the use of a construction in which the offset roller 407 is disposed inside the offset roller arm 406, but this difference in construction is merely a difference simply in design. That is, there is no difference in function and action from the construction shown in FIG. 4.

On the other hand, a sheet clamp member 412 exemplified as a holding member shown in FIG. 5 is adapted to hold down the trailing edge portion of the aligned sheet S from above it by the urging force of urging means (not shown). The sheet clamp member 412 is adapted so as to hold down the aligned sheet S from above it when the offset rollers 407 have been lifted up by the pickup solenoid 433 after completing the alignment in the width direction of the sheet S and the alignment of the tailing edge of the sheet S.

Thereby, the sheet S discharged (conveyed) earlier onto the treatment tray 410 can be held in a predetermined position without being subjected to the action such as an associated conveyance with a subsequent sheet S successively fed thereafter. Incidentally, the sheet clamp member 412 is rotated upward to receive the sheet S while the offset rollers 407 perform a reverse rotation as shown in FIG. 7.

The sheet bundle discharging member 413 exemplified as a discharging member shown in FIG. 5 discharges a treated sheet bundle onto the stack tray 421. The sheet bundle discharging member 413 holds the sheet clamp member 412 rotatably. Also, the sheet bundle discharging member 413 is adapted to move in a direction of the stack tray 421 provided downstream side of the treatment tray 410 shown in FIG. 8 while holding a sheet bundle, which has been aligned or stapled after being aligned, by the sheet clamp member 412.

Then, thereafter, the sheet bundle discharging member 413 is adapted so as, when arriving at a fore end portion of the treatment tray 410 as the sheet discharging position indicated by a solid line in FIG. 8, to release the holding of the sheet bundle SA with the sheet clamp member 412 on a stack tray 421 to discharge and stack the sheet bundle SA onto the stack tray 421. Incidentally, a holding member 421A shown in FIG. 2 is adapted to hold the sheet bundle SA thus discharged and stacked onto the stack tray 421.

Here, the sheet bundle discharging member 413 has motive power transmitted thereto by a sheet bundle discharging motor 430 through a rack and a pinion as shown in FIG. 5. Thereby, the sheet bundle discharging member 413 can be reciprocally moved between a position for discharging the sheet onto the stack tray 421 and its home position near the sheet trailing edge stopper 411. The sheet bundle discharging member 413 is ordinarily fixed in the home position by the excitation of the sheet bundle discharging motor 430.

In FIG. 5, a clamp solenoid 434 pivotally moves the sheet clamp member 412. The clamp solenoid 434, when the offset roller 407 stops rotating after it has conveyed the sheet, and when the offset roller 407 is moved in the width direction, is adapted to be turned on to thereby upwardly pivotally move the sheet clamp member 412 through a lever 434 a and a releasing lever portion 412 a provided on the sheet clamp member 412.

FIG. 9 is a block diagram showing the construction of the controlling portion of the sheet processing apparatus 400 of such a construction. FIG. 9 shows a CPU 100 as an example of control device in this embodiment. The CPU 100 has a ROM 110 therein. The ROM 110 has stored therein a program, etc. corresponding to a control procedure shown in FIGS. 10 and 11 which will be described later. The CPU 100 is adapted to read out and execute this program and control each portion.

Also, the CPU 100 contains therein a RAM 121 in which data for work and input data are stored, and the CPU 100 is adapted to perform the control with reference to the data contained in the RAM 121 on the basis of the aforementioned program. Further, sensors such as an entrance sensor 403 exemplified as a sheet detecting device and a sheet bundle discharge sensor 415 and a retention jam timer T for detecting a sheet retention within the sheet processing apparatus are connected to the input port of the CPU 100.

Further, motors and solenoids such as the conveying motor 431, the offset motor 432, the sheet bundle discharging motor 430, the pickup solenoid 433, the clamp solenoid 434 are connected to output ports of the CPU 100. The CPU 100 is adapted to control the loads of the various motors and solenoids connected to the output ports in accordance with the aforementioned program based on the states of the sensors.

Also, the CPU 100 is provided with a serial interface portion (I/O) 130, and is adapted to effect the giving and receiving of control data with (the controlling portion of) the image forming apparatus main body 500, and also perform the control of each portion on the basis of control data sent from (the controlling portion of) the main body 500 of the image forming apparatus through the serial interface portion (I/O) 130.

The main body 500 of the image forming apparatus recognizes the size of the sheet discharged from the sheet discharging portion 208. Owing to this, the controlling portion of the sheet processing apparatus 400, which is constituted of a micro computer system, can recognize the size of the sheet inserted into the treatment tray 410 by means of serial communication with the controlling portion of the main body 500 of the image forming apparatus.

In the present embodiment, the sheet bundle stacked on the stack tray 421 constitutes a portion of the treatment tray 410 and therefore, when the discharge of the sheet bundle SA is done from the treatment tray 410, the stack tray 421 is adapted to be lowered by a stack tray lifting/lowering motor 450 (see FIG. 9) until the uppermost surface of the stacked sheet bundle is substantially flush with the treatment tray 410.

Next, the residual sheet processing operation of the sheet processing apparatus 400 and the main body 500 of the image forming apparatus at turning on the power will be described with reference to the flow charts shown in FIGS. 10 and 11.

When the main body 500 of the image forming apparatus detects a sheet remaining in the apparatus (in the path) with a residual sheet detecting device (not shown) at turning on the power (“Y” in S1000), the main body 500 of the image forming apparatus discharges the sheet to the sheet processing apparatus 400 (S1001).

The CPU 100 of the sheet processing apparatus 400 (see FIG. 9) detects the sheet discharged from the main body 500 of the image forming apparatus by the entrance sensor 403 of the sheet processing apparatus 400. When the entrance sensor 403 turns on (“Y” in S1010), the CPU 100 activates the pickup solenoid 433. Owing to this, the offset rollers 407 supported by the offset roller arm 406 is pulled up and raised (S1020).

Next, the conveying motor 431 is turned on to drive the conveying rollers 405 and the offset rollers 407 provided on the sheet discharging path to rotate in the same sheet conveying direction as the discharge direction from the main body 500 of the image forming apparatus (S1030). Thereafter, the sheet arrives at the conveying roller 405 and there is brought about a state in which motive power is transmitted from the conveying roller 405 to the sheet, and the sheet is separated from the sheet discharging portion 208 (see FIG. 1) of the image forming apparatus main body 500, whereupon the delivery of the sheet is completed.

Next, the retention jam timer T is set to detect retained sheet (jammed sheet) in the sheet processing apparatus (S1040). Next, the CPU 100 conveys the sheet to the treatment tray 410 by 80 mm in this embodiment by the conveying roller 405 (S1050) and yet, turns the pickup solenoid 433 off before the sheet completely leaves the conveying roller 405, and makes the offset roller 407 lower onto the sheet with the aid of the gravitational force of the offset roller 407 (S1060).

Thereafter, the CPU 100 waits until the trailing edge of the sheet passes the entrance sensor 403 of the sheet processing apparatus to turn off the entrance sensor 403 (S1070). Then, when the entrance sensor 403 turns off (“Y” in S1070), the CPU 100 judges that the sheet is not jammed, and resets the retention jam timer T (S1090).

Also, the offset rollers 407 are caused to rotate for a predetermined period of time from the turning off of the entrance sensor 403 to convey the sheet S so that the trailing edge of the sheet moves to a predetermined position downstream of the sheet trailing edge stopper 411. Then, when the sheet S is conveyed to such a position, the CPU 100 stops the rotation of the conveying motor 431 to thereby stop the conveying rollers 405 and the offset rollers 407 (S1100).

In addition, when the entrance sensor 403 of the sheet processing apparatus does not turn off (N in S1070) even if the retention jam timer T has timed up (Y in S1150), the CPU 100 judges that a jam has occurred and enters into a jam mode (S1160).

Next, the CPU 100 turns the clamp solenoid 434 on at a point of time whereat the rotation of the offset roller 407 has been stopped (S1100), and as shown in FIG. 6B, opens the sheet clamp member 412 installed in the home position near the trailing edge stopper 411. Thereafter, the CPU 100 rotates the conveying motor 431 in a direction reverse to the conveying direction, and pulls back the sheet S by the offset roller 407 (S1120), and causes the trailing edge of the sheet to abut against the trailing edge stopper 411.

The amount of rotation of the offset roller 407 when the trailing edge of the sheet is abutted against the sheet trailing edge stopper 411 is set, with the skew feed of the sheet S occurring when it is conveyed from the main body 500 of the image forming apparatus taken into account. Therefore, in this embodiment, the rotation amount of the offset rollers 407 is prescribed to a rotation amount, in which the sheet can be conveyed somewhat more than the distance from a switch back point at which the conveyance of the sheet S is stopped to the sheet trailing edge stopper 411.

Next, the offset rollers are raised (S1130) and the sheet bundle discharging member 413 is caused to proceed in a direction of the stack tray 421 by the sheet bundle discharging motor 430 in a state that a sheet S is clamped (held) by the sheet clamp member 412 as shown in FIG. 8. Then, when the sheet bundle discharging member 413 arrives at the fore end portion of the treatment tray 410, the hold of the sheet by the sheet clamp member 412 is released on the stack tray 421 so that the sheet may be discharged onto the stack tray 421 (S1140).

In addition, after discharging the sheet as described above, the sheet bundle discharging member 413 is returned to its home position. Also, the pickup solenoid 433 is turned off to lower the offset rollers 407, and thus the series of the processing is terminated.

As described above, the CPU 100 is designed so as, when a residual sheet is conveyed from the main body 500 of the image forming apparatus at turning on the power, to cause the sheet bundle discharging member 413 to move to the position, in which the sheet is discharged onto the stack tray 421, while holding the residual sheet after the trailing edge of the residual sheet is aligned. Owing to this, even when the sheet size is unknown, the alignment of the residual sheet on the stack tray can be secured.

In this embodiment, although the CPU 100 reads out the program written on the RAM (or ROM) shown in the flow chart in FIGS. 10 and 11 to control the operation, a similar effect will also be obtained if design is made such that the processing in the control program is carried out by hardware.

Also, in the above description, the case where the CPU 100 of the sheet processing apparatus 400 controls the above process has been described. However, design may be made such that the controlling portion of the main body 500 of the image forming apparatus performs the above control.

As described in this embodiment, when a residual sheet is conveyed from the main body of the image forming apparatus at turning on the power, the discharging member is moved to the sheet discharging position, in which the sheet is discharged onto the second sheet stacking portion, while holding the residual sheet by the holding member after aligning the trailing edge of the residual sheet. Thereby, the stackability of the sheet when the residual sheet is discharged can be secured.

While the present invention has been described with reference to the exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefits of Japanese Patent Application No. 2005-328111, filed Nov. 11, 2005, which is hereby incorporated by reference herein in its entirety. 

1. A sheet processing apparatus comprising: a first sheet stacking portion connected to a main body of an image forming apparatus for stacking thereon a sheet conveyed from the main body of the image forming apparatus; a second sheet stacking portion provided downstream of said first sheet stacking portion with respect to a sheet conveying direction for stacking thereon the sheet discharged from said first sheet stacking portion after being treated on said first sheet stacking portion; a trailing edge aligning portion for aligning a trailing edge in the sheet conveying direction of the sheet stacked on said first sheet stacking portion; a discharging member having a holding member for holding the sheet, the trailing edge of which has been aligned by said trailing edge aligning portion, and while holding the sheet by said holding member, moving the sheet to a sheet discharging position, in which the sheet is discharged onto said second sheet stacking portion by releasing a holding by said holding member; and a control device for controlling said discharging member in such a manner that, when a residual sheet remains in the main body of the image forming apparatus and the residual sheet is conveyed at turning on a power for the main body of the image forming apparatus, a trailing edge of the residual sheet is aligned by said trailing edge aligning portion, and then the residual sheet is moved to the sheet discharging position while the residual sheet is held by said holding member.
 2. A sheet processing apparatus according to claim 1, wherein said trailing edge aligning portion is provided with a regulating member, which is provided upstream of said first sheet stacking portion with respect to the sheet conveying direction for regulating the trailing edge of the sheet, and a sheet conveying member, which is rotatable forward and reversely, for abutting the sheet against said regulating member by conveying the sheet, which is conveyed onto said first sheet stacking portion, in a direction reverse to the sheet conveying direction after conveying the sheet in the sheet conveying direction.
 3. A sheet processing apparatus according to claim 2, further comprising a sheet detecting device for detecting the trailing edge of the sheet conveyed from the main body of the image forming apparatus, wherein when said control devices judges that the sheet conveyed by said sheet conveying member has passed said regulating member based on a signal from said sheet detecting device, said control device controls a drive of said sheet conveying member so as to abut the sheet against said regulating member by rotating said sheet conveying member reversely.
 4. An image forming apparatus comprising: an image forming portion for forming an image on a sheet; and a sheet processing apparatus as recited in claim 1 for treating the sheet with the image formed by said image forming portion.
 5. An image forming apparatus according to claim 4, wherein said control device is provided in said sheet processing apparatus or a main body of said image forming apparatus.
 6. An image forming apparatus comprising: an image forming portion for forming an image on a sheet; and a sheet processing apparatus as recited in claim 2 for treating the sheet with the image formed by said image forming portion.
 7. An image forming apparatus according to claim 6, wherein said control device is provided in said sheet processing apparatus or a main body of said image forming apparatus.
 8. An image forming apparatus comprising: an image forming portion for forming an image on a sheet; and a sheet processing apparatus as recited in claim 3 for treating the sheet with the image formed by said image forming portion.
 9. An image forming apparatus according to claim 8, wherein said control device is provided in said sheet processing apparatus or a main body of said image forming apparatus.
 10. An image forming apparatus comprising: an image forming portion for forming an image on a sheet; a first sheet stacking portion for stacking thereon the sheet with the image formed by said image forming portion; a second sheet stacking portion provided downstream of said first sheet stacking portion with respect to a sheet conveying direction for stacking thereon the sheet discharged after being treated on said first sheet stacking portion; a trailing edge aligning portion for aligning a trailing edge in the sheet conveying direction of the sheet stacked on said first sheet stacking portion; a discharging member having a holding member for holding the sheet, the trailing edge of which has been aligned by said trailing edge aligning portion, and while holding the sheet by said holding member, moving the sheet to a sheet discharging position, in which the sheet is discharged onto said second sheet stacking portion by releasing a holding by said holding member; and a control device for controlling said discharging member in such a manner that, when a residual sheet remains upstream of said first sheet stacking portion with respect to the sheet conveying direction and the residual sheet is conveyed at turning on a power for the image forming apparatus, a trailing edge of the residual sheet is aligned by said trailing edge aligning portion, and then the residual sheet is moved to the sheet discharging position while the residual sheet is held by said holding member. 